1. Field of the Invention
The present invention relates to a valve control device for an internal combustion engine.
2. Description of the Prior Art
A conventional valve control device is disclosed, for example, in Japanese Patent laid-open publication No. 7 (1995) -286506. This conventional device includes a rotational cam shaft which is rotatably supported on a cylinder head, a first cam provided on the cam shaft, a second cam provided on the cam shaft and having a larger nose portion than that of the first cam, a rocker shaft which is supported on the cylinder head, a first rocker arm which is rotatably supported on the rocker shaft and which is oscillated round the rocker shaft in response to the first cam so as to open and close an intake or exhaust valve, a second rocker arm which is rotatably supported on the rocker shaft and which is oscillated round the rocker shaft in response to the second cam and connecting means for selectively connecting the second rocker arm to the first rocker arm.
In this device, when the first rocker arm is not connected to the second rocker arm, a lift characteristic of the intake or exhaust valve determined by the first cam is obtained. On the other hand, when the first rocker arm is connected to the second rocker arm, a lift characteristic of the intake or exhaust valve determined by the second cam is obtained. When the first rocker arm is not connected to the second rocker arm, the second rocker arm makes a lost motion.
In the above prior device, however, a lifter which is disposed on the cylinder head is additionally required only for ensuring such lost motion of the second rocker arm. Therefore, the number of the component parts of the valve timing control device is increased and the manufacturing cost thereof is also increased.